On March 7, 1995, approximately 1251 hours Pacific standard time, a Bell Helicopter Textron 230, N230LF, registered to and operated by Emanuel Hospital & Health Center, d/b/a Life Flight, and being flown by a certificated rotorcraft-rated airline transport pilot, sustained substantial damage when the tail rotor impacted a fence during landing at the University Hospital helipad, Portland, Oregon. The pilot and flight nurse were uninjured. Visual meteorological conditions prevailed and a VFR flight plan was in effect. The flight, which was a positioning flight for intended operations from the University Hospital, was to have been operated under 14CFR91. The pilot reported that the heliport perimeter fence extended horizontally about two feet out from the heliport surface to act as a person-catcher. The fence was built with an approximate 4 inch gap at mid-span. The tail rotor guard on the aircraft was able to slip down into the gap, which resulted in contact between the tail rotor and fence. The pilot believed that an accident would not have occurred if the gap had not been there in the fence.